Control of Rodents

ABSTRACT

Control of Rodents A particulate mixture for use in the control of rodents which comprises a mixture of a plurality of bait particles and a plurality of non-bait particles, wherein each bait particle comprises matter edible by a rodent and a rodenticide and wherein each non-bait particle comprises matter edible by a rodent and has a flavour different from the flavour of a bait particle and wherein the non-bait particles are distinguished from the bait particles by at least one physical characteristic selected from size, shape, surface texture and internal texture. A non-bait particulate food for rodents as use in the control of rodents, when presented in admixture with bait particles to rodents, to encourage consumption of the bait particles. Such non-bait particulate food comprises dry extruded pellets of cereal meal and dried powdered crustacean.

The present invention is concerned with the control of rodents,particularly infestations of rats or mice. It is, further, concernedwith non-bait particulate food for rodents for use in mixtures withparticulate bait and with such mixtures which may be used in rodentcontrol.

It is in the nature of rats and mice to forage for food, i.e. to roam insearch of food which is palatable and/or which offers a desirable ‘chew’or ‘bite’ texture. Although a rat or a mouse may show an initialinterest in a palatable bait which has been placed in its run, it may,because of its natural behaviour, lose interest in the bait, aftertaking only a small amount, in favour of looking for somethingdifferent.

Some currently-available rodenticides are effective because their lethaldose is achieved by accumulation inside the body of the rodent over aperiod of time such as where the rodent has taken bait on severaloccasions. Such rodenticides have been developed to overcome‘bait-shyness’, which term is used to describe the avoidance by rodentsof food sources which have made them sick.

It is desirable, in methods of rodent control, to encourage a rodent totake a greater amount of bait in a sitting. This has been attempted, forinstance, by improving the palatability, to the rodent, of the bait.However, attempts to encourage a greater take of the bait are frustratedby the natural desire of the rodent to forage for, and investigate,alternative and potentially more interesting sources of food.

The technical problem faced by the inventors is to provide a bait-systemfor rodents wherein the bait retains its initial attraction to therodents but which system is adapted to provide ongoing interest for therodents such that their natural desire to forage is satisfied. Thistechnical problem is solved by the present invention.

Accordingly, the present invention provides a particulate mixture foruse in the control of rodents which comprises a mixture of a pluralityof bait particles and a plurality of non-bait particles, wherein eachbait particle comprises matter edible by a rodent and a rodenticide andwherein each non-bait particle comprises matter edible by a rodent andhas a flavour different from the flavour of a bait particle and whereinthe non-bait particles are distinguished from the bait particles by atleast one physical characteristic selected from size, shape, surfacetexture and internal texture.

The present invention also provides a method of increasing theconsumption of bait particles by a rodent which bait particles comprisematter edible by a rodent and a rodenticide comprising mixing the baitparticles to be presented to the rodent with non-bait particles whichcomprise matter edible by a rodent and having a flavour different fromthe flavour of the bait particles and wherein the non-bait particles aredistinguished from the bait particles by at least one physicalcharacteristic selected from size, shape, surface texture and internaltexture.

From their research, the inventors have discovered that, surprisingly,the palatability and efficacy of a bait, provided in the form of aplurality of bait particles, is increased by including, in admixturewith the plurality of bait particles, a plurality of non-bait particleswhich have a flavour different from the flavour provided on the baitparticle and which are distinguished from the bait particles by at leastone physical characteristic selected from size, shape, surface textureand internal texture. It has been discovered that this provision of adifferent flavour and, for instance, different shape or texture, in thebait-containing mixture encourages the natural foraging behaviour of therodents but acts as an arrestant in that it provides ongoing interestfor the feeding rodents such that interest in the bait itself isstimulated with the result that more bait is taken at one sitting by therodents. We have found that the use of the present invention not onlyhelps to overcome neophobia in rodents (i.e. their wariness or distrustof new food sources, such as when a bait is introduced into their areaof activity) but also leads the rodents to consume a lethal dose of baitmore quickly.

As used herein, the term “bait” means matter edible by a rodent whichincludes or contains at least one rodenticide. The term “non-bait”, asused herein, means matter edible by a rodent and which does not includeor contain any rodenticide. With no compromise of the definitions of“bait” and “non-bait” given above intended, the words “comprises” and“comprising”, as used herein, are intended to mean “includes” and“including”, respectively, to the extent that the presence of one ormore other materials is not excluded.

As described above, the present invention provides, in one aspect, amixture of a plurality of bait particles and a plurality of non-baitparticles. Typically, the non-bait particles are present in the mixturein an amount in the range of from 2.5 to 10% by weight based on thecombined weight of the bait particles and non-bait particles. As theamount of non-bait particles in the mixture decreases below 2.5% byweight, the amount of bait particles consumed by a rodent in a sittingtends to fall and eventually approaches the ‘take’ that would beexpected in the case where no non-bait particles are present. The amountof non-bait particles in the mixture should, preferably, therefore, notbe lower than 2.5% by weight, based on the combined weight of baitparticles and non-bait particles, in order that the non-bait achieves agood arrestant effect. As the amount of non-bait particles in themixture increases above 10% by weight, the amount of bait particlesconsumed by a rodent in a sitting tends to fall, presumably because, asthe non-bait becomes more plentiful in the mixture, its ability tostimulate interest in the bait starts to fall. We have found that betterresults are obtained if the amount of the non-bait particles in themixture is in the range of from 3 to 7% by weight, based on the combinedweight of the bait particles and non-bait particles in the mixture.Optimum take by a rodent has been found to occur when the amount ofnon-bait particles in the mixture is about 5% by weight, based on thecombined weight of the bait particles and non-bait particles in themixture.

The bait particles may be granular, for instance, based on naturalgrain, for example whole wheat grain, cut wheat grain, oats or canaryseed, or may, alternatively, be extruded pellets formed by extruding apaste or meal containing ground or comminuted food, such as cereal, andwater and then cutting the extrudate into pellets followed by drying.Such granular or pelleted material is treated with one or morerodenticidally-active agent in accordance with conventional procedures.According to a preferred embodiment, the bait particles are cut wheatgrain (typically having a size of approximately 1.5-2 mm by 1.5-2 mm)which is treated with one or more rodenticidally-active agent. Anyrodenticidally-active material may be used in the bait particles of theparticulate mixture of the invention. The rodenticidally-active materialmay be an anticoagulant rodenticide or may be a non-anticoagulantrodenticide. Examples of anticoagulant rodenticides that may be used inthe bait particles include one or more of difenacoum, brodifacoum,flocoumafen, bromadiolone, difethialone, warfarin, coumatetralyl,chlorophacinone, diphacinone, coumachlor, coumafuryl and pindone. Apreferred anticoagulant rodenticide for use in the present invention isdifenacoum. Examples of non-anticoagulant rodenticides that may be usedin the bait particles of the particulate mixture according to theinvention include vitamin D (ergocalciferol or cholecalciferol) andalphachlorolose. Preferably, the non-anticoagulant rodenticide isergocalciferol or chlolecalciferol or a mixture thereof. Preferably, thebait particles are selected from whole grain wheat, cut wheat grain andextruded pellets of ground wheat which bait particles are treated with arodenticide which, preferably, is difenacoum or vitamin D(ergocalciferol or cholecalciferol). Typically, the rodenticide used inthe invention will be used in the form of a concentrate whichadditionally contains a human taste deterrent, e.g. denatonium benzoate.In such a case, it will be apparent that, ignoring any addition of extraflavouring agent to the non-bait particles, there will always be adifference in flavour between bait particles containing a human tastedeterrent and the non-bait particles not containing this.

The non-bait particles, as described above, do not containrodenticidally-active agent. They provide a flavour different from theflavour of the bait particles used in the mixture. In one embodiment,the non-bait particles are prepared by extruding a paste comprisingground cereal, preferably ground wheat, water and flavouring agent,cutting the extruded paste into pellets and subjecting the pellets todrying. Preferably, the cereal paste will also contain dextrose sincethis not only sweetens the pellet and, therefore, itself provides aflavour component to the pellet but also acts as a binder for the groundcereal such that the pellets retain integrity and resist crumbling. Morepreferably, the extruded pellets comprise, after drying, approximately95% ground wheat and approximately 5% dextrose.

The flavouring agent will typically be one that also provides thenon-bait particles with an odour, in addition to a flavour, differentfrom that of the bait particles. We have found that good results areobtained using, as the flavouring agent for the non-bait particles,berries, e.g. a wildberry mixture; fruit, e.g. apple, banana, pear;meat, e.g. comminuted meat or a meat extract; faeces or a constituent offaeces, such as skatole; peppermint; vanilla; fish meal; yeast;chocolate and dried powdered crustacean. Preferably, the flavouringagent is chocolate or dried, powdered crustacean or their mixtures.Dried, powdered, crustacean is especially preferred.

The non-bait particles used in the particulate mixture of the inventionwill contain an amount of flavouring agent which is sufficient toachieve interest from the rodents and to confer, on the non-baitparticles in the mixture, an arrestant effect. In general, the non-baitparticles will contain from 5 to 4000 ppm of flavouring agent dependingon the actual flavouring agent used. We have found that the optimumlevel of flavouring agent content in the non-bait particles does dependon the actual flavouring agent used since different flavouring agentsprovide different levels of flavour sensation and olfactory stimulationin rodents. The optimum content levels of some of the flavouring agentsthat may be used in the non-bait particles are as follows:—

Optimum content Flavouring agent (based on weight of non-bait particle)skatole 0.001% (10 ppm) yeast 0.002% (20 ppm) wildberry 0.0025% (25 ppm)meat extract 0.020% (200 ppm) dried powdered crustacean 0.030% (300 ppm)chocolate 0.200% (2000 ppm)

It will be apparent, from the above, that the typical practical range offlavouring agent content of the non-bait particles depends on the actualflavouring agent used. For instance, it is possible to identify atypical practical range of flavouring agent content wherein the lowerlimit of the content range is the content which is sufficient to achievea strong interest from the rodents and the upper limit of the contentrange is the point above which no significant further increase inarrestant effect is achieved. Thus, a typical content of skatole will bein the range of from 5 to 50 ppm, with about 10 ppm being preferred. Atypical content of wildberries will be in the range of from 10 to 150ppm, with about 25 ppm being preferred. A typical content of meatextract will be in the range of from 100 to 700 ppm, with about 200 ppmbeing preferred. A typical content of dried powdered crustacean is inthe range of from 150 to 900 ppm, with about 300 ppm being preferred. Atypical content of chocolate will be in the range of from 500 to 4000ppm, with about 2000 ppm being preferred.

As stated above, we have found that not only must the non-bait particleshave a flavour different from the bait particles in the mixture but alsothat the non-bait particles must be distinguishable from the baitparticles by at least one physical characteristic selected from size,shape, surface texture and internal texture. This distinction isessential so that the mixture of edible particles provides the rodentswith variety to maintain their interest. Our research suggests that therodents' natural desire to forage can substantially be satisfied if thenon-bait particles used in the mixture of the invention have an appealto all of the senses of taste, touch and sight and, preferably, also thesense of smell. Since rodents appear to investigate potential food bytouch, for instance by picking up the food using their front paws, aswell as by taste and/or odour, the non-bait particles will preferably bedistinguishable from the bait particles by their shape and/or sizeand/or surface texture. Rodents are known to like a hard multi-edgeshape to gnaw at and, thus, hardness, as well as shape and/or sizeand/or surface texture, should preferably also be taken into account inthe non-bait particle design. If the bait particles comprise extrudedpellets, and the non-bait particles also comprise extruded pellets, theshape and/or size of the bait particles and the shape and/or size of thenon-bait particles should be different such that the rodents candistinguish between the bait particles and the non-bait particles.According to a preferred embodiment of the invention, the non-baitparticles will be distinguishable from the bait particles because oftheir different size. We have found that we have obtained good resultsusing non-bait particles in the form of extruded pellets having roughlya circular cross-section and having a length of from 8 to 12 mm and adiameter of about 4 mm which are distinguishable from bait particlesbased on whole wheat grain, cut wheat grain, oats, canary seed, orextruded pellets having similar dimensions to such whole or cut grains.

We have found that excellent results are obtained by using, in thecontrol of rodents, a mixture of bait particles, selected from wholewheat grains and cut wheat grains treated with difenacoum, with aplurality of non-bait particles wherein the amount of non-bait particlesin the mixture is from 3 to 7% by weight, preferably about 5% by weight,based on the total weight of the bait particles and non-bait particlesand wherein the non-bait particles comprise dried, pelletted, extrudedground wheat and from 150 to 900 ppm, preferably about 300 ppm, ofdried, powdered crustacean or from 500 to 4000 ppm, preferably about2000 ppm, of chocolate. Preferably, the flavouring agent will, however,be dried powdered crustacean. Accordingly, this composition and themethod of using it form preferred embodiments of the invention.

It has, further, been discovered by the inventors, to their surprise,that rodents, particularly rats, show a preference for non-baitparticles flavoured with dried, powdered crustacean compared to non-baitparticles flavoured with other flavouring agents. To the knowledge ofthe inventors, this has not been disclosed in the prior art. Accordingto a further aspect, the present invention also provides a non-baitparticulate food for rodents for admixture with bait particles in thecontrol of rodents which non-bait particulate food comprises dryextruded pellets of cereal meal, preferably ground wheat, and dried,powdered crustacean, said non-bait particulate food, when presented inadmixture with bait particles to rodents, encourages consumption of thebait particles by the rodents. Especially advantageous results may beachieved when the flavoured non-bait particulate food has at least onephysical characteristic selected from size, shape, external surfacetexture and internal texture which is different from that of theparticulate bait with which it is to be admixed. Preferably, thenon-bait particulate food will be distinguishable from the particulatebait with which it is to be admixed by virtue of particle size. The useof such a flavoured non-bait particulate food in admixture with baitedwheat grain has been found, in tests carried out on rats, to double thepalatability of the bait particles.

DESCRIPTION OF EXPERIMENTS

A series of laboratory pen trials were carried out. In these trials,semi-wild rats (Rattus novegicus) and, separately, semi-wild mice (Musdomesticus) were used in a semi-wild environment.

In each case, the following test diets were provided for consumption bythe rodents and, in all cases, a control diet is also provided. Theamount of take by the rodents of the test diets and the control diet wasmonitored and rodent death was also monitored.

In the experiments, the palatability ratio of the diets under test wasdetermined. The palatability ratio is defined as follows:—

${{palatability}\mspace{14mu} {ratio}} = \frac{{total}\mspace{14mu} {test}\mspace{14mu} {bait}\mspace{14mu} {eaten}}{{total}\mspace{14mu} {control}\mspace{14mu} {diet}\mspace{14mu} {eaten}}$

We prefer, for effective control in the field to be achieved, that thepalatability ratio is at least 0.3 for rats and is at least 0.1 formice.

EXPERIMENT 1 Test Diet 1

Cut cereal bait treated with difenacoum (Neosorexa Cut Wheat bait, SotexLimited).

Test Diet 2

A mixture of cut cereal bait treated with difenacoum (Neosorexa CutWheat bait, Sorex Limited) and non-bait pellets (5% by weight based ontotal weight of bait pellets and non-bait pellets). The non-bait pelletscomprised dried, extruded pellets (length about 1 cm, diameter about 4mm) containing about 95% by weight ground wheat, about 5% by weightdextrose and 300 ppm dried, powdered crustacean.

In the feeding experiments, the palatability of the test diets wasassessed. This was done by determining the amount of test diet taken bythe rodent and also the amount of control diet taken by the rodent. Thepalatability ratio of the test diet was determined as the amount of testdiet taken divided by the amount of control diet taken. The resultsshown below are the average of ten tests.

Test Diet No. Palatability Ratio Rat 1 1.42 2 3.61 Mice 1 0.67 2 1.52

The results obtained demonstrate that the palatability was increased(more than doubled) for both the rats and the mice by including non-baitparticles flavoured with dried, powdered crustacean with the baitparticles.

After the rodents had finished eating the Test Diet 2, it was found thatthe content of the non-bait particles in the mixture had been reducedfrom 5% by weight to less than 1% by weight. This was found for both therats and the mice in the tests. However, in eating the Test Diet 2, therodents had consumed double the amount of bait particles compared toTest Diet 1.

EXPERIMENT 2

In this experiment, tests were carried out to investigate whether theincrease in palatability demonstrated in EXPERIMENT 1 above is merelythe result of the use of the flavouring agent. The palatability ratiosshown in the results below were averaged from ten tests.

Test Diet 1

Cut cereal bait treated with difenacoum (Neosorexa Cut Wheat bait, SorexLimited) identical to that used in Test Diet 1 in EXPERIMENT 1 exceptthat it additionally contains 300 ppm dried, powdered crustacean.

Test Diet 2

This was identical to the Test Diet 2 used in EXPERIMENT 1 above.

Palatability Ratio Test Diet No. Rats Mice 1 1.54 0.66 2 3.61 1.52Statistical Analysis P = 0.004 sig. diff. P = 0.0008 sig. diff.

The results show that the bait particles containing the dried powderedcrustacean flavour are not as palatable to rats and mice asnon-flavoured bait particles but used in admixture with non-baitparticles flavoured with the dried powdered crustacean. Thus, theconclusion is that the crustacean flavour should be provided on anon-bait particle (used together with bait) rather than simply on thebait in order to increase the palatability of the bait significantly.

EXPERIMENT 3

In this experiment, tests were carried out to investigate whether theincrease in palatability demonstrated in the earlier experiments is aresult of merely mixing bait particles with non-bait particles (neitherthe bait particles nor the non-bait particles have added flavour) or theuse of a different flavour on the non-bait particles. The palatabilityratios shown below were averaged from ten tests.

Test Diet 1

A mixture of cut cereal bait treated with difenacoum (Neosorexa CutWheat bait, Sorex Limited) with dried extruded pellets (length about 1cm; diameter about 4 mm) containing about 95% by weight of ground wheatand about 5% by weight of dextrose with no added flavouring agent. Theamount of non-bait pellets in the mixture was 5% by weight based on thetotal weight of the bait pellets and non-bait pellets.

Test Diet 2

This was the same as the Test Diet 2 used in EXPERIMENT 1 above.

Palatability Ratio Test Diet No. Rats Mice 1 2.53 1.34 2 3.61 1.52Statistical Analysis P = 0.27 No sig. diff. P = 0.61 No sig. diff.

The results show that, especially in rats, the crustacean flavourprovided on the non-bait particles is essential to increase palatabilityof the bait particles.

EXPERIMENT 4

This experiment was carried out to study the effect of using aparticulate mixture in palatability tests on rats and mice in which thenon-bait particles which contain dextrose but no additional flavouringagent have approximately the same size as the bait particles (althoughthey do have a slightly different shape compared to the bait particles).The test diets used in this experiment were as follows: —

Test Diet 1

This was identical to Test Diet 1 in EXPERIMENT 1 above. Test Diet 2

A mixture of cut cereal bait treated with difenacoum (Neosorexa cutwheat bait, Sorex Limited) and non-bait pellets which had been ground toapproximately the same size as the cut cereal bait (2.5% by weight basedon the total weight of the cut wheat bait and the ground non-baitpellets). The non-bait pellets were produced as described in Test Diet 2of EXPERIMENT 1 except that no dried, powdered crustacean was included.After the pellets had been dried, they were subjected to grinding toreduce the pellet size such that it was approximately the same as thatof the cut cereal bait.

Test Diet 3

A mixture of cut cereal bait and ground non-bait pellets as describedabove in Test Diet 2 of this experiment except that the mixturecontained 5% of the ground non-bait pellets (based on the total weightof cut cereal bait and ground non-bait particles).

In the feeding experiments carried out using rats and mice, thepalatability of the test diets was assessed. This was done bydetermining the amount of test diet taken by the rodent and also theamount of control diet taken by the rodent. The palatability ratio ofthe test diet was determined as the amount of test diet taken divided bythe amount of control diet taken. The palatability ratios shown in thetable below were averaged from ten tests. The results were alsosubjected to statistical analysis.

Palatability Ratio Study No. Diet Rats Mice 1. TEST DIET 1 1.02 0.67TEST DIET 2 0.95 1.06 Statistical Analysis P = 0.92 P = 0.48 2. TESTDIET 1 1.02 1.05 TEST DIET 3 1.22 1.58 Statistical Analysis P = 0.40 P =0.49

The results obtained in this experiment indicate that the presence ofthe ground non-bait particles in the mixture with the cut cereal baitdid slightly increase palatability in the 5% addition level for rats andin both the 2.5% and 5% addition levels for mice. Statistical analysisof these results, however, indicates that the incorporation of theground non-bait pellets did not give rise to significantly increasedpalatability.

EXPERIMENT 5

This experiment was carried out on mice only using canary seed baitparticles and using ‘mini’ non-bait particles. The test diets used inthis experiment were as follows: —

Test Diet 1

Canary seed treated with calciferol (as rodentically-active agent).

Test Diet 2

Canary seed treated with calciferol (as rodentically-active agent) and300 ppm dried, powdered crustacean.

Test Diet 3

A mixture of canary seed treated with calciferol with ‘mini’ dried andextruded non-bait pellets (5% by weight based on the total weight of thecanary seed bait and ‘mini’ non-bait pellets).

The ‘mini’ non-bait pellets comprised 95% by weight ground wheat, about5% by weight dextrose and 300 ppm dried, powdered crustacean. The meanlength of the “mini” pellets, taken from a random sample of ten “mini”pellets ranging from 2.4 mm to 4.2 mm in length, was 3.67 mm. The meandiameter of the “mini” pellets, taken from a random sample of ten “mini”pellets ranging from 2.3 mm to 2.4 mm in diameter, was 2.33 mm.

The palatability ratios were determined in accordance with the proceduredescribed in EXPERIMENT 4. The results shown below are, in each case,the average of ten tests.

Study No. TEST DIET Palatability Ratio 1 1 0.34 2 2 0.36 3 3 1.13Statistical Analysis Study 1 vs Study 2, P = 0.93 Study 1 vs Study 3, P= 0.14 Study 3 vs Study 2, P = 0.20

The results obtained demonstrate that although palatability was notincreased by incorporating the flavouring agent into the canary seedbait particles, palatability was increased using TEST DIET 3, a mixtureof bait particles and flavoured non-bait particles.

EXPERIMENT 6

The test diets used in this experiment were:—

Test Diet 1

Cut cereal bait treated with difenacoum (Neosorexa Cut Wheat bait, SorexLimited).

Test Diet 2

A mixture of bait (Test Diet 1, as described above) and non-baitpellets. The amount of non-bait pellets in the mixture was 5% by weight(based on the combined weight of the bait and the non-bait pellets). Thenon-bait pellets comprised dried, extruded pellets (length of about 1cm, diameter of about 4 mm) containing about 95% by weight ground wheat,about 5% by weight dextrose and 300 ppm dried, powdered crustacean.

The feeding experiment involved 20 rats. 10 rats were provided access toTest Diet 1 and 10 rats were provided access to Test Diet 2. The dailytake of the diets by the rats was measured and the amount of activeingredient ingested per rat was calculated. The number of rats that hadingested a lethal dose (2×LD50 dose) by each day was also calculated.The results are shown in the following table.

% Rats ingested a lethal dose Day Test Diet 1 Test Diet 2 0 0 0 1 0 60 280 100 3 90 100 4 100 100The results are also shown graphically in FIG. 1.

As indicated above, both baits resulted in all rats consuming a lethaldose. However, the time taken for the rats to eat a lethal dose (2×LD50)of the bait was much quicker with Test Diet 2 (containing the flavourednon-bait pellets) than with Test Diet 1 (bait only). The use ofparticulate mixtures of bait and non-bait pellets according to theinvention is expected to lead to quicker control in the field.

1. A particulate mixture for use in the control of rodents whichcomprises a mixture of a plurality of bait particles and a plurality ofnon-bait particles, wherein each bait particle comprises matter edibleby a rodent and a rodenticide and wherein each non-bait particlecomprises matter edible by a rodent and has a flavour different from theflavour of a bait particle and wherein the non-bait particles aredistinguished from the bait particles by at least one physicalcharacteristic selected from size, shape, surface texture and internaltexture.
 2. A particulate mixture according to claim 1, wherein thenon-bait particles are present in the mixture in an amount in the rangeof from 2.5 to 10% by weight, preferably in the range of from 3 to 7% byweight, based on the combined weight of the bait particles and non-baitparticles.
 3. A particulate mixture according to claim 2, wherein theamount of non-bait particles in the mixture is about 5% by weight basedon the combined weight of bait particles and non-bait particles.
 4. Aparticulate mixture according to claim 1, wherein the bait particles arecereal based, typically selected from whole wheat grain, cut wheatgrain, oats, canary seed and cereal based pellets treated with arodenticide.
 5. A particulate mixture according to claim 1, wherein therodenticide is difenacoum or vitamin D.
 6. A particulate mixtureaccording to claim 1, wherein the non-bait particles are extrudedpellets comprising ground wheat.
 7. A particulate mixture according toclaim 6, wherein the extruded pellets have a length of from 8 to 12 mmand a diameter of about 4 mm.
 8. A particulate mixture according toclaim 1, wherein the non-bait particles comprise a flavour componentselected from chocolate, dried powdered crustacean, yeast, faeces, fishmeal, meat, berries and mixtures of two or more of these.
 9. Aparticulate mixture according to claim 8, wherein the flavour componentis selected from chocolate, dried powdered crustacean and mixturesthereof.
 10. A particulate mixture according to claim 9, wherein theflavour component comprises dried powdered crustacean.
 11. A particulatemixture according to claim 9, wherein the flavour component is presentat a concentration in the range of from 150 to 900 ppm based on theweight of the non-bait particles.
 12. A particulate mixture according toclaim 11, wherein the flavour component is present at a concentration ofabout 300 ppm based on the weight of the non-bait particles.
 13. Amethod of increasing the consumption of bait particles by a rodent whichbait particles comprise matter edible by a rodent and a rodenticidecomprising mixing the bait particles to be presented to the rodent withnon-bait particles which comprise matter edible by a rodent and having aflavour different from the flavour of the bait particles and wherein thenon-bait particles are distinguished from the bait particles by at leastone physical characteristic selected from size, shape, surface textureand internal texture.
 14. A non-bait particulate food for rodents foradmixture with bait particles in the control of rodents which non-baitparticulate food comprises dry extruded pellets of cereal meal and driedpowdered crustacean, said non-bait particulate food, when presented inadmixture with bait particles to rodents, encourages consumption of baitparticles.